WO2021221666A1

WO2021221666A1 - Touch/pen sensor surfaces

Info

Publication number: WO2021221666A1
Application number: PCT/US2020/030765
Authority: WO
Inventors: Iii Fred Charles Thomas; Robert Scott RAWLINGS; Sarah D. BURTON
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2020-04-30
Filing date: 2020-04-30
Publication date: 2021-11-04

Abstract

An example computing device includes a plurality of separate touch/pen (T/P) sensor surfaces to generate analog position information. The computing device also includes a single analog-to-digital (A-to-D) controller to control the plurality of sensor surfaces in a multiplexed manner and generate digital position information based on the analog position information.

Description

TOUCH/PEN SENSOR SURFACES

Background

[0001] Some computing devices employ touch-based input methods that allow a user to physically touch, for example, an associated display, and have that touch registered as an input at the particular touch location, thereby enabling a user to interact physically with objects shown on the display of the computing device. Digital pens may also be used in conjunction with computing devices and provide a natural and intuitive way for users to input information into applications running on the computing devices.

Brief Description of the Drawings

[0002] Figure 1 is a diagram illustrating a touch/pen sensor system according to an example.

[0003] Figure 2 is a block diagram illustrating elements of the sigma-delta analog-to-digital controller shown in Figure 1 according to an example.

[0004] Figure 3 is a layer diagram illustrating layers of a touch/pen sensor according to an example.

[0005] Figure 4 is a block diagram illustrating a computing system with a touch/pen sensor system according to an example.

[0006] Figure 5 is a block diagram illustrating a computing device according to an example. [0007] Figure 6 is a flow diagram illustrating a method of sensing position according to an example.

[0008] Figure 7 is a block diagram illustrating a computing device according to another example.

Detailed Description

[0009] In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific examples in which the disclosure may be practiced. It is to be understood that other examples may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims. It is to be understood that features of the various examples described herein may be combined, in part or whole, with each other, unless specifically noted otherwise.

[0010] Some examples disclosed herein are directed to a computing device that combines a plurality of touch/pen (T/P) sensor surfaces and a single analog-to- digital (A-to-D) sampling controller. The term “touch/pen” or “T/P” sensor as used herein includes touch-based interfaces, pen-based interfaces, and interfaces that are both touch-based and pen-based.

[0011] Each of the sensor surfaces may comprise a projected capacitive (p-cap) sensor. Some example material types for this sensor include, but are not limited to, indium-tin-oxide (ITO), silver nanowire, metal mesh, carbon nano-tube, and poly(3,4-ethylenedioxythiophene) (PEDOT) film. These sensor films are clear, electrically-conductive layers that may be fabricated into a row and column p- cap sensor array, and that may be formed on a clear plastic layer (e.g., polyethylene terephthalate (PET)) or a clear glass substrate.

[0012] The A-to-D sampling controller may be a sigma-delta A-to-D sampling controller that has drive and sense electrodes operated in parallel and that aggressively filters out noise from the measured voltage-based capacitive signals. An example sigma-delta A-to-D sampling controller is able to filter out p-cap noise, while operating at high frequency touch/pen image capture rates (e.g., 600 frames per second). This avails the opportunity for this touch/pen controller type to be multiplexed among several p-cap sensors at a rate fast enough to provide temporal performance that is without noticeable latency for human computer interaction, for example.

[0013] In some examples, the sigma-delta controller is able to image a single touch sensor surface at between 100 and 600 frames per second. Each of the sensor surfaces may be implemented in either a touch/pen display screen, a touch/pen whiteboard, an indirect inking device, or a touch pad. In some examples, the plurality of sensor surfaces are coupled to the A-to-D sampling controller via a multiplexer, which allows a single sigma-delta controller to operate two T/P p-cap sensors simultaneously at half the rate of the controller’s full operational rate (e.g., each operated at 300 frames per second). In an example, operating two T/P p-cap sensors with a single controller in this manner results in lower cost, lower power consumption, and fewer components with a smaller product size.

[0014] In some examples, an electronic device, such as a notebook or foldable computer, may include dual touch display screens that are operated simultaneously in a multiplexed mode using a single sigma-delta controller. In other examples, an electronic device, such as a notebook computer, may include a touch display screen and a deck-based touch pad that are operated simultaneously in a multiplexed mode using a single sigma-delta controller.

[0015] Figure 1 is a diagram illustrating a touch/pen sensor system 100 according to an example. System 100 includes a plurality of T/P devices 102A and 102B, multiplexer 110, and sigma-delta analog-to-digital (A-to-D) controller 116. In an example, T/P devices 102A and 102B are touch displays. In another example, T/P devices 102A and 102B are touch pads. In another example, T/P devices 102A and 102B include a touch display and a touch pad. Although two T/P devices 102A and 102B are shown in Figure 1 , other examples may include more than two such devices. An example includes four touch displays configured together into a large scribing surface, such as whiteboard, which is coupled to the controller 116 via the multiplexer 110.

[0016] Device 102A includes a plurality of sense electrodes 104A, a plurality of drive electrodes 106A, and a plurality of capacitive nodes 108A. The sense electrodes 104A are conductive traces represented by a plurality of equally spaced vertical lines, and the drive electrodes 106A are conductive traces represented by a plurality of equally spaced horizontal lines. The intersections of the sense electrodes 104A and the drive electrodes 106A correspond to the locations of the capacitive nodes 108A.

[0017] Device 102B includes a plurality of sense electrodes 104B, a plurality of drive electrodes 106B, and a plurality of capacitive nodes 108B. The sense electrodes 104B are conductive traces represented by a plurality of equally spaced vertical lines, and the drive electrodes 106B are conductive traces represented by a plurality of equally spaced horizontal lines. The intersections of the sense electrodes 104B and the drive electrodes 106B correspond to the locations of the capacitive nodes 108B.

[0018] The sense electrodes 104A and 104B and drive electrodes 106A and 106B may be used to sense the position of a finder, pen tip, or other object. In some examples, the sense electrodes 104A and 104B and drive electrodes 106A and 106B are about 4-5mm wide, with a pitch of about 100mm. Sensing of position of a digital pen with a fine tip (e.g., about 0.5mm to 2mm diameter or less) may involve triangulation of tip location using multiple signals from the trace intersections closest to the pen tip point touch down location, and other trace crossings surrounding the touch down location.

[0019] The sense electrodes 104A are coupled via communication link 109A to a first set of inputs of multiplexer 110. In an example, communication link 109A includes a separate conductive line for each of the sense electrodes 104A. The sense electrodes 104B are coupled via communication link 109B to a second set of inputs of multiplexer 110. In an example, communication link 109B includes a separate conductive line for each of the sense electrodes 104B. [0020] The drive electrodes 106A are coupled via communication link 111A to a third set of inputs of multiplexer 110. In an example, communication link 111A includes a separate conductive line for each of the drive electrodes 106A. The drive electrodes 106B are coupled via communication link 111 B to a fourth set of inputs of multiplexer 110. In an example, communication link 111 B includes a separate conductive line for each of the drive electrodes 106B.

[0021] Multiplexer 110 includes a first set of switches 112 (represented by a single switch to simplify the figure) that selectively couples either the first set of inputs of the multiplexer 110 or the second set of inputs of the multiplexer 110 to the communication link 113. The switches 112 thereby selectively couple either the sense electrodes 104A or the sense electrodes 104B to the controller 116 to provide sense signals to the controller 116.

[0022] Multiplexer 110 includes a second set of switches 114 (represented by a single switch to simplify the figure) that selectively couples either the third set of inputs of the multiplexer 110 or the fourth set of inputs of the multiplexer 110 to the communication link 115. The switches 114 thereby selectively couple either the drive electrodes 106A or the drive electrodes 106B to the controller 116 to provide drive signals from the controller 116 to the drive electrodes. In some examples, the controller 116 controls the switches 112 and 114.

[0023] In the illustrated example, the multiplexer 110 is a 2:1 multiplexer that selectively couples two T/P devices 102A and 102B to a single controller 116.

In another example, the multiplexer 110 may be a 4:1 multiplexer that selectively couples four T/P devices to the single controller 116. Each of the switches represented by the switches 112 and 114 may be high speed electronically based (transistor based) single-pole double-throw (SPDT) switches.

[0024] In some examples, each of the T/P devices 102A and 102B may include at least one p-cap indium-tin-oxide (ITO), silver nanowire, metal mesh, carbon nano-tube, or PEDOT film. Figure 2 is a block diagram illustrating elements of the sigma-delta analog-to-digital (A-to-D) controller 116 shown in Figure 1 according to an example. In an example, controller 116 includes a hybrid analog/digital application specific integrated circuit (ASIC) 202 and a digital field programmable gate array (FPGA) 204. ASIC 202 includes closed-loop touch line current driver 206, sigma-delta converter with 1-bit digital to analog converter (DAC) 208, and sensor driver 212. FPGA 204 includes digital signal processor (DSP) 210 and host interface 214. It is noted that the controller 116 shown in Figure 2 is an example of a sigma-delta p-cap touch/pen imaging controller, and in other examples, controller 116 may be configured differently than shown in Figure 2.

[0025] In an example, ASIC 202 is an analog front-end (AFE) with a data rate of about 300 to 600 frames per second (i.e. , 300 to 600Hz), and ASIC 202 drives and reads up to 64 channels in parallel. For example, if the controller 116 is operated at 500Hz, and two T/P devices (e.g., devices 102A and 102B) are coupled to the controller 116 via the multiplexer 110, each of the T/P devices may be completely sampled at 250Hz. As another example, if the controller 116 is operated at 500Hz, and four T/P devices are coupled to the controller 116 via the multiplexer 110, each of the T/P devices may be completely sampled at 125Hz. As another example, if the controller 116 is operated at 600Hz, and twelve T/P devices are coupled to the controller 116 via the multiplexer 110, each of the T/P devices may be completely sampled at 50Hz. The controller 116 may switch between the various T/P devices cyclically.

[0026] Closed-loop touch line current driver 206 is coupled to sensor driver 212 to facilitate the generation of drive signals. Sensor driver 212 outputs analog drive signals via communication link 115. The closed-loop drive current on each electrode supports long electrodes and electrode variability. In some examples, the drive signals provide increased channel isolation and noise suppression. [0027] Closed-loop touch line current driver 206 receives analog sense signals via communication link 113 and provides the analog sense signals to sigma- delta converter 208. In some examples, the driving and sensing of each electrode occurs individually and in parallel. Sigma-delta converter 208 performs a delta-sigma modulation process and converts the analog sense signals into digital sense signals, which are output to DSP 210.

[0028] In some examples, sigma-delta converter 208 encodes analog signals using high-frequency delta-sigma modulation, and then applies a digital filter to form a higher-resolution but lower sample-frequency digital output. Delta-sigma modulation involves delta modulation in which the change in the signal (i.e., its delta) is encoded, resulting in a stream of pulses. Accuracy of the modulation may be improved by passing the digital output through a 1-bit DAC and adding (sigma) the resulting analog signal to the input signal (the signal before delta modulation), thereby reducing the error introduced by the delta modulation. [0029] DSP 210 performs filtering of the digital sense signals received from sigma-delta converter 208, and touch/pen image extraction. DSP 210 provides full touch/pen images to host interface 214. In some examples, DSP 210 also performs touch processing (e.g., finger/pen coordinates, palm rejection, gesture interpretation, etc.). In an example, host interface 214 outputs the full touch/pen images via a communication link 215 or conversely it provides touch/pen coordinate information universal serial bus (USB)/inter-integrated circuit (I2C) human interface device (HID) packets to a host device. In some cases, host interface 214 may provide both touch image as well as USB/I2C HID packets to a host device.

[0030] Figure 3 is a layer diagram illustrating layers of a touch/pen sensor 300 according to an example. Sensor 300 includes removable polymer textured scribing tactile layer 302, optically clear adhesive (OCA) layer 304, cover clear plastic or glass layer 306, OCA layer 308, sensor layer with pen/touch p-cap sensor traces 310, clear plastic layer 312, and sensor layer with pen/touch p- cap sensor traces 314. In an example, layer 302 has a thickness of 75um; layer 304 has a thickness of 50um; layer 306 has a variable thickness; layer 308 has a thickness of 50um; Iayer 310 has a thickness of 0.1um to 0.5um; Iayer 312 has a thickness of 100um; and layer 314 has a thickness of 0.1 urn to 0.5um. [0031] Layers 310, 312, and 314 represent a p-cap sensor stack. In some examples, the drive conductive traces (i.e. , drive electrodes) for the sensor stack are in layer 310, and the sense conductive traces (i.e., sense electrodes) for the sensor stack are in layer 314. The p-cap sensor (e.g., PEDOT) layers 310 and 314 are clear, electrically-conductive layers that are fabricated into row and column p-cap sensor arrays, which are formed on a clear plastic or glass layer (e.g., polyethylene terephthalate (PET) or soda-lime glass), such as layer 312. The fabrication process may include increasing the surface resistance of portions/areas of the PEDOT film by orders of magnitude via wet-printing of the PEDOT film with a chemical agent. In contrast, fabrication processes for other materials typically involve adding trace material to the layer or etching material off the layer. Compared to other materials that have been used for T/P sensor surfaces, example PEDOT films are less expensive, have a lower index of refraction, are more flexible/bendable, and have a lower variance in sheet resistance across the layer, which is typically about plus or minus two percent. Example PEDOT films have an index of refraction of 1.5. In contrast, example ITO films have an index of refraction of 2.1. Sheet resistance is a measure of resistance of thin films that are nominally uniform in thickness. Sheet resistance is a special case of resistivity for a uniform sheet thickness. The units for sheet resistance are ohms per square. The highly uniform sheet resistance (e.g., a variance in sheet resistance of less than plus or minus 5%) of the PEDOT layer translates into nodes having a more uniform capacitance over the layer than materials with a higher variance in sheet resistance (e.g., higher than plus or minus 5%).

[0032] Figure 4 is a block diagram illustrating a computing system 400 with a touch/pen sensor system according to an example. System 400 includes processor 402, memory 404, input devices 412, output devices 414, and touch/pen (T/P) sensor system 416. Processor 402, memory 404, input devices 412, output devices 414, and T/P sensor system 416 are communicatively coupled to each other through communication link 410. In an example, T/P sensor system 416 may be implemented with the T/P sensor system 100 shown in Figure 1. T/P sensor system 416 represents a T/P-enabled interface that enables T/P-based interaction between a user and a display, or between a user and some other T/P based device, such as a touch pad.

[0033] Processor 402 includes a central processing unit (CPU) or another suitable processor. In an example, memory 404 stores machine readable instructions executed by processor 402 for operating system 400. Memory 404 includes any suitable combination of volatile and/or non-volatile memory, such as combinations of Random-Access Memory (RAM), Read-Only Memory (ROM), flash memory, and/or other suitable memory. These are examples of non-transitory computer readable media (e.g., non-transitory computer-readable storage media storing computer-executable instructions that when executed by at least one processor cause the at least one processor to perform a method). The memory 404 is non-transitory in the sense that it does not encompass a transitory signal but instead is made up of at least one memory component to store machine executable instructions for performing techniques described herein.

[0034] Memory 404 stores T/P input processing module 406. Processor 402 executes instructions of T/P input processing module 406 to perform techniques described herein.

[0035] Input devices 412 include a keyboard, mouse, data ports, stylus or digital pen, and/or other suitable devices for inputting information into system 400. Output devices 414 include speakers, data ports, and/or other suitable devices for outputting information from system 400.

[0036] T/P sensor system 416 may track the position of, for example, a user’s finger, a stylus, or a digital pen, on a display and/or touch pad, and output corresponding touch information to T/P input processing module 406 for processing. The input device may be any elongated device that a user may hold and touch to a surface, such as a touch display or an active area of a tablet computing device.

[0037] An example is directed to a computing device. Figure 5 is a block diagram illustrating a computing device 500 according to an example.

Computing device 500 includes a plurality of separate touch/pen (T/P) sensor surfaces 502 to generate analog position information. Computing device 500 also includes a single analog-to-digital (A-to-D) controller 504 to control the plurality of sensor surfaces in a multiplexed manner and generate digital position information based on the analog position information.

[0038] Each of the sensor surfaces 502 may include a projected capacitive array type sensor. The sensor may be fabricated from one of a variety of sensor materials, including but not limited to, (p-cap) poly(3,4-ethylenedioxythiophene) (PEDOT) film. The A-to-D controller 504 may be a sigma-delta A-to-D sampling controller. The sensor surfaces 502 may be implemented in separate touch display screens. The sensor surfaces 502 may be implemented in a touch display screen and a touch pad. The sensor surfaces 502 may be coupled to the A-to-D controller via a multiplexer. Each of the sensor surfaces 502 may include an indium-tin-oxide (ITO), silver nanowire, metal mesh, carbon nano tube, or PEDOT film.

[0039] The sensor surfaces 502 may include at least three separate sensor surfaces. The sensor surfaces may include at least two separate sensor surfaces implemented adjacent to each other in a single touch display screen. The sensor surfaces may include at least four separate sensor surfaces implemented adjacent to each other in a single touch display screen.

[0040] Another example is directed to a method of sensing position. Figure 6 is a flow diagram illustrating a method 600 of sensing position according to an example. At 602, the method 600 includes generating analog position information with a plurality of separate touch/pen (T/P) sensor surfaces. At 604, the method 600 includes controlling the plurality of sensor surfaces with a single analog-to-digital (A-to-D) controller in a multiplexed manner to generate digital position information based on the analog position information.

[0041] Each of the sensor surfaces in method 600 may include a projected capacitive array type sensor. The sensor may be fabricated from PEDOT film or another material. The A-to-D controller in method 600 may be a sigma-delta A- to-D sampling controller.

[0042] Another example is directed to a computing device. Figure 7 is a block diagram illustrating a computing device 700 according to another example. Computing device 700 includes a plurality of separate projected capacitive touch/pen (T/P) sensor surfaces 702 to generate analog position information. Computing device 700 includes a multiplexer 704 coupled to the sensor surfaces to receive the analog position information and selectively output the analog position information. The computing device 700 also includes an analog-to-digital (A-to-D) controller 706 to control the plurality of sensor surfaces and generate digital position information based on the analog position information output by the multiplexer. [0043] Each of the sensor surfaces 702 may include a projected capacitive array type sensor, and the A-to-D controller 706 may be a sigma-delta A-to-D sampling controller.

[0044] Although specific examples have been illustrated and described herein, a variety of alternate and/or equivalent implementations may be substituted for the specific examples shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific examples discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.

Claims

1. A computing device, comprising: a plurality of separate touch/pen (T/P) sensor surfaces to generate analog position information; and a single analog-to-digital (A-to-D) controller to control the plurality of sensor surfaces in a multiplexed manner and generate digital position information based on the analog position information.

2. The computing device of claim 1 , wherein each of the sensor surfaces comprises a projected capacitive array type sensor.

3. The computing device of claim 1 , wherein the A-to-D controller is a sigma-delta A-to-D sampling controller.

4. The computing device of claim 1 , wherein the sensor surfaces are implemented in separate touch display screens.

5. The computing device of claim 1 , wherein the sensor surfaces are implemented in a touch display screen and a touch pad.

6. The computing device of claim 1 , wherein the sensor surfaces are coupled to the A-to-D controller via a multiplexer.

7. The computing device of claim 1 , wherein each of the sensor surfaces comprises an indium-tin-oxide (ITO), silver nanowire, metal mesh, carbon nano tube, or poly(3,4-ethylenedioxythiophene) (PEDOT) film.

8. The computing device of claim 1 , wherein the sensor surfaces include at least three separate sensor surfaces.

9. The computing device of claim 1 , wherein the sensor surfaces include at least two separate sensor surfaces implemented adjacent to each other in a single touch display screen.

10. The computing device of claim 1 , wherein the sensor surfaces include at least four separate sensor surfaces implemented adjacent to each other in a single touch display screen.

11. A method, comprising: generating analog position information with a plurality of separate touch/pen (T/P) sensor surfaces; and controlling the plurality of sensor surfaces with a single analog-to-digital (A-to-D) controller in a multiplexed manner to generate digital position information based on the analog position information.

12. The method of claim 11 , wherein each of the sensor surfaces comprises a projected capacitive array type sensor.

13. The method of claim 11 , wherein the A-to-D controller is a sigma-delta A- to-D sampling controller.

14. A computing device, comprising: a plurality of separate projected capacitive touch/pen (T/P) sensor surfaces to generate analog position information; a multiplexer coupled to the sensor surfaces to receive the analog position information and selectively output the analog position information; and an analog-to-digital (A-to-D) controller to control the plurality of sensor surfaces and generate digital position information based on the analog position information output by the multiplexer.

15. The computing device of claim 14, wherein each of the sensor surfaces comprises a projected capacitive array type sensor, and wherein the A-to-D controller is a sigma-delta A-to-D sampling controller.